Work hard, sacrificing time for painting (3)
I believe the answer is:
oil
'painting' is the definition.
(oil painting is a kind of painting)
'work hard sacrificing time' is the wordplay.
'work hard' becomes 'toil' (to toil is to do strenuous work).
'sacrificing' is a deletion indicator.
'time' becomes 't' (abbreviation).
'toil' with 't' removed is 'OIL'.
'for' is the link.
(Other definitions for oil that I've seen before include "painting" , "Liquid gold" , "Liquid fuel" , "Lubricant or petroleum" , "Grease" .)